Re: [PATCH] mm: skip CMA pages when they are not available

[Zhaoyang Huang]

On Wed, Apr 19, 2023 at 2:07 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote:
>
> "zhaoyang.huang" <zhaoyang.huang@xxxxxxxxxx> writes:
>
> > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> >
> > It is wasting of effort to reclaim CMA pages if they are not availabe
> > for current context during direct reclaim. Skip them when under corresponding
> > circumstance.
>
> Do you have any performance number for this change?
Sorry, No. This patch arised from bellowing OOM issue which is caused
by MIGRATE_CMA occupying almost 100 percent of zones free pages and
solved by "168676649 mm,page_alloc,cma: conditionally prefer cma
pageblocks for movable allocations". This could be a common scenario
for a zone that has a large proportion of CMA reserved page blocks
which need to be considered in both allocation and reclaiming
perspective.

04166 < 4> [   36.172486] [03-19 10:05:52.172] ActivityManager: page
allocation failure: order:0, mode:0xc00(GFP_NOIO),
nodemask=(null),cpuset=foreground,mems_allowed=0
0419C < 4> [   36.189447] [03-19 10:05:52.189] DMA32: 0*4kB 447*8kB
(C) 217*16kB (C) 124*32kB (C) 136*64kB (C) 70*128kB (C) 22*256kB (C)
3*512kB (C) 0*1024kB 0*2048kB 0*4096kB = 35848kB
0419D < 4> [   36.193125] [03-19 10:05:52.193] Normal: 231*4kB (UMEH)
49*8kB (MEH) 14*16kB (H) 13*32kB (H) 8*64kB (H) 2*128kB (H) 0*256kB
1*512kB (H) 0*1024kB 0*2048kB 0*4096kB = 3236kB
......
041EA < 4> [   36.234447] [03-19 10:05:52.234] SLUB: Unable to
allocate memory on node -1, gfp=0xa20(GFP_ATOMIC)
041EB < 4> [   36.234455] [03-19 10:05:52.234] cache: ext4_io_end,
object size: 64, buffer size: 64, default order: 0, min order: 0
041EC < 4> [   36.234459] [03-19 10:05:52.234] node 0: slabs: 53,
objs: 3392, free: 0
>
> Best Regards,
> Huang, Ying
>
> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> > ---
> >  mm/vmscan.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index bd6637f..04424d9 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -2225,10 +2225,16 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
> >       unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
> >       unsigned long skipped = 0;
> >       unsigned long scan, total_scan, nr_pages;
> > +     bool cma_cap = true;
> > +     struct page *page;
> >       LIST_HEAD(folios_skipped);
> >
> >       total_scan = 0;
> >       scan = 0;
> > +     if ((IS_ENABLED(CONFIG_CMA)) && !current_is_kswapd()
> > +             && (gfp_migratetype(sc->gfp_mask) != MIGRATE_MOVABLE))
> > +             cma_cap = false;
> > +
> >       while (scan < nr_to_scan && !list_empty(src)) {
> >               struct list_head *move_to = src;
> >               struct folio *folio;
> > @@ -2239,7 +2245,10 @@ static unsigned long isolate_lru_folios(unsigned long nr_to_scan,
> >               nr_pages = folio_nr_pages(folio);
> >               total_scan += nr_pages;
> >
> > -             if (folio_zonenum(folio) > sc->reclaim_idx) {
> > +             page = &folio->page;
> > +
> > +             if (folio_zonenum(folio) > sc->reclaim_idx ||
> > +                     (get_pageblock_migratetype(page) == MIGRATE_CMA && !cma_cap)) {
> >                       nr_skipped[folio_zonenum(folio)] += nr_pages;
> >                       move_to = &folios_skipped;
> >                       goto move;